1. Field of the Invention
The present invention relates to an apparatus for observing an arc of a lamp, and more particularly, to an apparatus for observing an arc of a lamp by which it is possible to easily observe the degree to which a lamp electrode is damaged.
2. Description of Related Art
An exposing apparatus is used to manufacture semiconductor devices which are used in various electronic equipment and flat panel displays such as a liquid crystal display. The exposing apparatus is provided with a lamp for emitting light by an arc discharge and a lamp arc observing apparatus for observing whether the lamp is damaged.
Referring to FIG. 1 showing a conventional lamp arc observing apparatus, a lamp 20 and a parabolic reflective mirror 30 for reflecting and focusing the light emitted from the lamp 20 are installed in a frame 10. An arc discharges when power is applied to a pair of electrodes 20a and 20b of the lamp 20. The light emitted by the arc discharge is reflected by the parabolic reflective mirror 30 and proceeds to a main mirror 40. The light reflects from the main mirror 40 and travels through an opening 10b of the frame 10 and is used as desired.
As the lamp 20 is used for a long time, the electrodes 20a and 20b become damaged or abraded due to the high operating temperatures and the gap distance between the electrodes 20a and 20b increases. Damage to the electrodes 20a and 20b can be observed through a first observing hole 30a and a second observing hole 10a respectively formed in the parabolic reflective mirror 30 and the frame 10.
It is very difficult to form the first observing hole 30a without damaging the parabolic reflective mirror 30 since the parabolic reflective mirror 30 is formed of glass-like material. Also, the efficiency of light use of the lamp 20 suffers since light leaks through the first observing hole 30a.